Hydropneumatic apparatus for developing and maintanining hydrostatic pressure



2,536,881 APPARATUS FOR DEVELOPING AND E R U s S E R D Em M T T Y L R w B H G G N I C N H M T MN AM WM DA 0 R m 1 5 9 1 2 Jan.

Filed May 16, 1946 3 Sheets-Sheet l INVENTOR M 18. ATTORNEY Jan. 2, 1951 G. B. LYTLE v HYDROPNEUMATIC APPARATUS FOR DEVELOPING AND MAINTAINING HYDROSTATIC PRESSURE A I 3 Sheets-Sheet 2 Filed May 16, 1946 IN VEN TOR fiagg e 3. Kylie nnorepygY Jan. 2 1951 G. B. LYTLE 2,536,831

HYDROPNEUMATIC APPARATUS FOR DEVELOPING AND MAINTAINING HYDROSTATIC PRESSURE Filed May 16, 1946 3 Sheets-Sheet 3 INVENTOR N R Mi M ATTORNEY Patented Jan. 2, 1951 UNITED STATES EATENT OFFICE.

HYDROPNEURIATIC APPARATUS FGR DEW VELOPING AND MAENTAINING HYDRO:- S'EATIC PRESSURE Application May 16, 1946, Serial No. 570,272-

1 Claim. 1.

This invention relates to systems for developing andmaintaining hydrostatic pressure, particularly for use in industrial installations in which it is desired to obtain close control of the operation of'hydraulic rams and presses, and alsotoa novel combination of a simplex doubleacting hydraulic pumpand; a double-acting air cylinder constructed and arranged for balanced operation from a common source of pneumatic pressure.

Among the objects of. the invention is to prm videa hydraulicpressure-developing and utilizing system capable of -developing hydraulic power for presses or similar devices and for testing boilers and other vessels ona closed system and which eliminates the necessity of utilizing bypass valves; orother power-consuming pump controls when a, predetermined pressure is reached.

Another object of the invention is to provide a hydrostatic pressure-developing system capable of operating atsuch a rate of speed as to compensate for. leaks and maintain a constant predetermined; pressure after: a desired predeterminedpressure isv reached.

Another object of the-invention is to provide a hydraulic pressure-developing system capable of developing and holding a predetermined hydrostatic pressure and of" automatically coming into action on; but a slight reduction of the-pressure developed'and: desired to be maintained. Another objectoftheinvention is to. provide a novel. power and pumping assembly comprising acdouble-actingpneumatic cylinder for providing power; and a simplex double-acting hydraulic pump so arranged in relation to each other as to; maintain hydraulic pressure were. longholding-i period and respond automatically to restore the desired holding pressure immediately upon slight-diminution of the desired holding pressure; due'to the leakage from valves, paclrings, connections; etc; v Other objects involving novel constructions and combinations of parts will appear inthe specification in which I have set forth what I now consider the best mode of applying thepr nciplesormvi ven mn- Referring-to thedrawings.

Fig. 1 is; anelevational View of a power and pumping. assembly;

Fig. 2'is a schematic diagram of the power and pumping assembly in one form of. hydraulicpressure developing and utilizing system;

Fig. 3 is a schematic diagram of the powerand pumping assembly in another form ofhyd'raulicpressure developing and utilizing system;

'. Figs. 4 and5 are sectional views, respectively, j

2 of the upper and lower. portions of'the powerand pumping assembly;

Fig; 6 is anelevational view of means for controlling the application of. compressed airor other fluid medium alternately to opposite sides of the piston. of the power'unit'; and i Fig. 7 is an elevationalv view taken from the right side of'Fig. 6.

Asshown in Figs. 1, 4 and 5, the; pump is a simplex double-acting pump comprising a unitary cylinder or cylinder block" It having secured: to its lower end a flanged ring H; which is fastened to a plate 92 by cap screws. Plate I 2 iszpart of a frame which. includes four standards secured at their upper ends to the corners of plate l2 and secured at their lower ends to a. base plate. I3. Two of the standards M and l5 are illustrated in Fig. l. A'third; plate I6? is fastened to the stand:- ards intermediate the upper-'andlower plates I2 and is;

The power unit- H is secured to plate I 6- by means of a number of bolts depending from plate l6 and passing'through the upper and lower cylinder heads is and IQ ofthe cylinder 29 of the power unit. Cylinder 20. has a port 2| in the upper cylinder head it and a port 22 in the lower cylinder head it, Fig. 5-. The frame by which the pump cylinder it" and the power cylinder 2-43 are supported holds these cylinders in spaced relation with the axes of the cylinders in alignment. The power unitisdouble-acting'andhasa piston 23 to which a piston rod 24 is attached.

The piston rod extends from. the upper surface of the piston through a stufling box 25, as shown in Fig. 5.

The unitary pump cylinder Ill-is bored from either end to provide upper-and" lower chambers 26 and 21-, respectively, Fig. 4. Chamber is provided with an inlet port 28 and an outlet port 29. Chamber 2''! is provided with an inlet port 33 and anoutlet port-3i. The respective chambers contain plungers 32' and 33 which are tied together for unitary operation so that one plunger enters its chamber as the other plunger is: retracted from its chamber.- The upper end of chamber 26 is closed byplunger 32 and a guide ring 34 which snugly engages the interior of the chamber and provides a bearing surface for the plunger. The upper end of cylinder block Ii) is enlarged and accommodates a bushing 35 by which the plunger 32 is-laterally supported; This bushing serves as a bearing for the plunger. Bushing 35 is held in place by a cross-bar 35 which isbolted toafianged ring 31 by means of bo s, 3 3ml 9, Cross-bar36 "is iastened'in fixed moves upwardly and downwardly.

relation to the cylinder block l and plunger 32 freely extends through opening 49 in the crossbar. The upper end of plunger 32 is in threaded engagement with a yoke 42.

The lower plunger 33 is mounted for reciprocation in its chamber 21. Plunger 33 extends downwardly through a guide ring 43, Fig. 5, and a bushing 44 which closes the enlarged opening 45 at the lower end of the cylinder block it. Bushing 44 is held in place by a cross-bar it which is bolted to the flange of ring H by means of a pair of bolts 48, 49.

Flange ring H is secured to the lower end of cylinder block and to the upper plate l2 of the supporting frame. The lower end or" the plunger 33 is threaded at 59 and engaged to a yoke 5|. Yokes 42 and 5| are tied together by means of a pair of connecting rods 52, 53, each of which is secured at its ends to the yokes so that the two plungers will work together. The two connecting rods are slidably guided by flanged rings H and 31. A threaded rod 54 connects yoke 5| with piston rod 24. This threaded rod is in engagement with a threaded bore 55 in the yoke and a threaded bore 58 in the end of the piston rod. When the position of the piston with respect to the plungers is correctly adjusted the threaded rod 54 is locked in position by nuts 51, 58. 59 is a cam disk whose position on the threaded rod is adjustable to time the operation of the valves which control the supply of fluid pressure to the power unit, as will be explained hereinafter.

As illustrated in Figs. 6 and '7, the flow of compressed air or of other elastic fluid to the upper 1 and lower ends of the power unit is controlled by a pair of valves 60, El. These valves are operated by cam 59 when it reaches the upper and lower ends of the stroke of the piston. The compressed air is applied from a source (not shown) and the delivery pressure is controlled by a pressure-reducing valve 62. The air pressure is provided through conduit 63 and is efiective upon valves 69 and 6! through conduits 64 and es, re-

spectively. As shown in Fig. 6, cam 59 has reached the upper end of its stroke and the control button 66 is depressed. In this position air travels through conduit 54, control valve 65, conduit 61 and into port 68 of the remote control valve 69. The plunger in this remote control valve is thereby moved to the left. This permits the air to pass from conduit 63 through conduit 79, remote control valve 59, conduit II, to port 2| at the upper end of power cylinder 29. At the same time port 22 at the lower end of the power cylinder 20 and conduit 12 are opened to the atmosphere by remote control valve 69 to allow the air in the lower part of power cylinder 29 to escape as the piston is forced downwardly.

The air which is entering the top of the power cylinder 29 will drive the piston down until the cam 59 depresses the button 13 of valve 6 I. When this occurs, the plunger in remote control valve 69 is moved to the right by the air pressure operating through conduit 65, valve BI, conduit 74 and port 15. With the plunger within remote control valve 59 to the right, air flows through conduit E9, remote control valve 69, conduit 12 and port 22 to the under side of piston 23, and as the piston moves upwardly, the air above the piston is exhausted through port 2!, conduit H,

and remote control valve 59, to the atmosphere.

This cycle of operation is repeated as the piston If the cam 59 should happen to be in an intermediate p sition after operation has been discontinued, the pump can be put into operation by manually pressing one of the buttons 65 and 13 after the air pressure has been turned on. The button valves and the remote control valve are of standard constructions.

The valve system assures constant application of power during the full cycle of the pump. There is no interruption of air supply to one side of piston 23 until after the button at the end of a stroke has been depressed. After the button has been depressed the air from the button valve immediately reverses the position of the plunger in the remote control valve and the air piston is driven in the opposite direction under the same pressure that obtained during the previous stroke. The pneumatic pressure for supplying the power cylinder may be adjusted to a desired operating pressure by the reducing valve in the line supplying the power cylinder. As the piston travels, plungers 32 and 33 of the pump successively operate to compress and reject the hydraulic fluid contained in their chambers 26 and 27 of the pump.

The operation of the power and pumping unit is such as to maintain a desired hydraulic pressure in conduit it on the discharge side of the pump, Fig. 2, with which both pump chambers 25 and 27 are connected. Plunger 32 maintains the pressure as it moves downwardly and plunger maintains the pressure as it moves upwardly. Liquid is drawn into the upper chamber 26 through port 28 and conduit 19 during the upstroke of plunger 32, and liquid is drawn into chamber 2'! through port 30 and conduit during the down stroke of plunger 33. The power and pumping unit is immediately responsive to restore and maintain the desired hydraulic pressure on slight diminution of the hydraulic pressure due to the leakage from valves, packings, connections, etc., in the hydraulic system. The sensitivity of response to a drop in hydraulic pressure in the system is accomplished by arranging the power cylinder and the plungers of the pump in vertical alignment with the power cylinder lowermost and the piston of the power cylinder connected to the plungers of the pump. With this arrangement, though the same eifective pneumatic force is delivered to the piston during successive strokes, the same pressure is developed in each of the hydraulic chambers of the pump because the effect of the reduced area of the upper surface of the piston is compensated by the weight of the moving parts. The balance thereby obtained imparts a floating characteristic to the moving parts whereby stalling due to inertia is avoided and equal sensitivity in both directions of the stroke is eifected. The valves for controlling the application of pneumatic pressure to opposite sides of the piston is under the control of the piston and there is no interruption of supply to the cylinder except for subjecting the alternate ends of the piston to pressure for reversing the stroke.

The relationship of the pump and the power cylinder is such that practically any hydraulic pressure can be obtained, depending upon the pneumatic pressure and the ratio of the diameters of the power cylinder and of the hydraulic plungers. If it is desired to develop and maintain a hydrostatic pressure of 2,000 lbs. per square inch, for example, the units are so proportioned as to produce this hydraulic pressure while operating under a given pneumatic pressure and come to rest when the desired hydraulic pressure the developedii hydrostatic pressure,- whichever" side of the penumatic piston is-atthe timesub jected topressure, will cause the pump and-thepower unit immediately 'to' reactand buil d -upthe original-pressure; which-is, in the example noted; 2, 000? lbs: per' square inch; In other systems; power" has. necessarily been consumed during a" pressureholding period because of such factors as the loss ofpower'involved in converting energy into= power for-operating auxiliary controls, bypassing througha relief Va1ve, the friction in a relief valve andthe needt'o cool" the liquid. As a: consequence, .the invention; effects economiesrin operation, as well as more dependable holding power for maintaining apredeterminedhydraulic pressure requisite for many industrial operationS. Thehydraulic system illustrated in Fig.-

includes 'a closed reservoir 8-2containing compressed are orothen elastic-fluid medium-irrits upper -portion, and-a non-compressible fluidmediuminits lower portion. This non-compressible fluid medium=may constitute-water; oil; or a mixture of soluble oil" and water. This non-compressible fluid medium is-distributedthroughoutthe; corrduits; pump'a-ndpiston-chambered a press? The lowerend of the reservoir-is connected byia'cond'uit 83; valve 84-anda-conduit 6,5 to thepiston chamber 86*of the-press. Conduit 81, connected to conduit 85, is connected to conduit I8 through a valve 88. Conduit 18 is connected through valve 89 with conduit 99 through which fluid pressure may be delivered to the pressure side of pistons 9I and 92 by which movable platen 93 is moved away from fixed platen 94. Conduit 90 has connection with conduit 95, and the liquid contained in reservoir 82 through valve 96. Supply check valves 97 and 98 are interposed between conduit 95 and conduits 19 and 89, respectively, leading to the upper and lower chambers of the pump. Discharge check valves 99 and I80 are interposed between conduit I8 and the upper and lower chambers, respectively, of the pump. When the press is in open position at the start of a press-operating cycle, the valves are disposed as follows: valve 84 open; valve 88 closed; valve 89 open; valve 95 closed. The pressure developed by the pump is thereby communicated to pistons 9| and 92. To close the press on low pressure, the valves are disposed in the following positions: valve 84 open; valve 88 closed; valve 89 closed; valve 96 open. With this arrangement of the valves, the ram-chamber 86 is actuated and subjected to pressure by fluid flowing from reservoir 82 through conduit 8385, and the liquid in the retracting cylinders is expelled to conduit 90-95. For some operations it is desirable to momentarily release the pressure for gassing purposes, as when molding plastics and rubber, and this may be accomplished at low pressure by leaving valve 84 open and valve 88 closed, closing valve 96 and opening valve 89, thereby subjecting the pistons 9| and 92 to the pressure of the pump. The valve 89 may be momentarilyopened and closed for varying the effective pressure on the moving platen 93.

To close the press on high pressure, the valves are disposed as follows: valve 84 closed; valve 88 open; valve 89 closed; valve 96 open. With this arrangement ofum he valves, full pressure of the pump is delivered through conduit 8! to the ram and the liquidgexpelled by retracting pistons 9I and 92 is transmitted to conduit 90'-95 and the 8. reservoir."- rermomentarily gassing? on:

84 open; valve 88 closed; valve w open ;valve==96 closed; The ramis thereby cutioff' from-the pressure-developedby =the pump and Y the pump press, sure is directed-i to retracting pistons: 9-I and-19.2, valve 96 being closed to prevent the' flow of liquid;

from-the retractingeylinders to. thereservoir: To

again close *tliepress on high pressure; the. dispo sition of the valves-for:obtaininghigh pressureas pressure operable on the pistons" off thepress is maintained substantially constant;

The hydraulic system illustrated Y in Fig: 31 1mcludesa reservoir I 9 I which is partiallyfilled'fiwith hydraulic-fluid and vented" to" the atmosphere: The. pressure. condition for low pressure. press operation is established by the headcf'f' liquid! within the reservoir. The lower end 'of' the resene voir-i's connected. by a'conduit: I93,- val've: I [wand conduit. I85'to the ram or'pistomchamberr'lfli of'thepress. Conduit I'IJBiS connectedthrouglr valve I III- with conduit I98 from which=a= branch connection I99extendsto the pressure-sides offthe: auxiliarylifting pistons II IFand' II I-'. Conduit'IOB is connected through valve I I2 to conduit I I3 having branch connections with discharge check valves II 4 and H5, of the pump. Supply check valves H6 and II! are connected to conduit II8 which is connected to conduit I93, and thereby connected to the bottom of the supply reservoir IIII.

When the press is in an open position at the start of a press operating cycle, the valves are disposed as follows: valve I84 open; valve I81 open; valve H2 closed. In this condition the press is open and subjected only to the hydrostatic head of fluid in reservoir II on pistons I96, I I9 and III. To close the press the valves are disposed as follows: valve I04 open; valve I0] closed; valve II2 open. With this arrangement the hydraulic pressure developed by the pump is applied to the auxiliary lifting cylinders III] and III. The ram chamber I66 is maintained full by the flow of liquid from reservoir IOI. For

momentarily relieving the pressure on the press, as when it is desired to gas a mold, the valves are disposed as follows: valve I94 open; valve I 91 open; valve II2 closed. In this arrangement the hydraulic pressure developed by the pump is shut off but pressure is maintained on the press by the hydrostatic head of fluid in reservoir IQI acting upon the auxiliary lifting pistons I I0 and HI and the ram II9. To close the press on high pressure the valves are disposed as follows: valve I04 closed; valve I91 open; valve I I2'open. The full hydraulic pressure developed by the pump is then applied to the auxiliary lifting pistons and to the main ram. At the completion of the pressing operation the press is opened by restoring all the valves to their initial positions as described for the start of the cycle.

In both both systems illustrated in Figs. 2 and 3, all of the valves may be closed at ;the same time for safety purposes, and also for. settingup dies, as in molding plastics and rubber;

By closing all of the valves atone time the oper pressure the valves are disposed as=.f"ollbws: valves ator can stop the travel of the movable platen in any position.

. What is claimed is:

i In a pressure supply apparatus for supplying liquid under pressure to an hydraulic system in order to develop a definite pressure, a doubleacting pump having aligned bores with inlet and outlet ports and a pair of oppositely acting plungers of substantially equal diameters connected together forsuccessively pumping liquid under the same pressure from their respective bores upon reciprocation of the plungers, a power supply system including a double-acting pneumatic cylinder motor having connections with piping and a pressure reducing valve for controlling the pressure of air from the piping to said pneumatic cylinder motor, means controlled by said plungers and including valves for automatically making effective the controlled air pressure upon opposite sides of the piston of the pneumatic motor always to apply constant pressure to one side or the other of the piston to move or to hold the piston, depending upon any change or lack of change in the hydraulic pressure desired to be developed in the bores of the double-acting pump, the plungers of said pneumatic cylinder motor being connected in line with the piston of the pneumatic motor and disposed vertically with the pneumatic motor located below the hydraulic pump and the combined weight of the plunger-s and piston and their connected moving parts being effective against the pneumatic pressure required to hold or move the piston upwardly and supplementary to the pneumatic pressure efiective to hold or move the piston downwardly so that the piston and connected plungers are substantially equally responsive to a constant pneumatic pressure exerted on either the upper or lower surface of the pneumatic piston and the hydraulic pressure developed by the plungers of the associated pump is maintainable substantially constant over a relatively long period.

GEORGE B. LYTLE.

REFERENCES CITED The following references are of record in the file of this patent:

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